1. Field of the Invention
The present invention relates to a cleaner, and more specifically to a cleaner that is used to remove residues after chemical mechanical polishing for planarizing a substrate during semiconductor manufacturing.
2. Description of the Related Art
Semiconductor devices are fabricated through complex multiple processes. Chemical mechanical planarization (CMP) is a semiconductor manufacturing process for planarizing various substrates currently used for the fabrication of semiconductor devices with design geometries of less than 0.35 microns.
CMP involves holding and rotating a thin flat substrate of a semiconductor material against a wetted polishing surface under suitable pressure and temperature conditions. A chemical slurry containing alumina or silica particles can be used as an abrasive. The chemical slurry contains selected chemicals, which etch various substrate surfaces during processing. In this polishing process, the combination of mechanical removal and chemical removal of material is suitable to achieve good surface planarization.
However, CMP may leave contaminants on the surface of the semiconductor substrate. Most of the contaminants are abrasive particles composed of alumina or silica and reactive chemicals added to the polishing slurry. The contaminant layer may include reaction products of the polishing slurry and the polished surface. It is thus necessary to remove the contamination sources before subsequent processing of the semiconductor substrate in order to avoid the introduction of defects causing deterioration in semiconductor device reliability and low fabrication process yield. Under such circumstances, post-CMP cleaning solutions have developed to clean substrate surfaces on which CMP residues are present.
Alkaline solutions based on ammonium hydroxide have been usually used as post-CMP cleaners and most of them are used to clean surfaces containing aluminum, tungsten, tantalum, and oxides.
Copper is currently replacing aluminum as an optimal substance for the production of interconnects. Following CMP of a copper-containing substrate, copper, copper oxides, and slurry particles from the polishing solution may exist on the copper surface. The copper surface can diffuse rapidly in silicon and silicon dioxide. Accordingly, it should be removed from all wafer surfaces to prevent device failure.
However, a typical post-CMP cleaning solution effective in alumina- and silica-based CMP is not effective in cleaning copper-containing surfaces. The cleaning solution is liable to damage copper. Further, the cleaning efficiency of the post-CMP cleaning solution has proven unacceptable.
Korean Patent Publication No. 10-2003-0025238 discloses a cleaning solution for copper post-CMP including a quaternary ammonium hydroxide, a C2-C5 polar organic amine, a corrosion inhibitor, and water wherein the cleaning solution has an alkalinity exceeding 0.073 milliequivalents base per gram of solution. However, the cleaner has a low etch selectivity for copper/copper oxide films, resulting in low cleaning ability.
Thus, there is a need for a cleaner that protects a pure metal, such as copper metal, used in a semiconductor device and effectively removes oxide films on the surface of the metal.